It’s simply a fact that worrying about the future means worrying twice, once for sure, and maybe again IF it should happen.
Yours is a very interesting comment, Rebekah. (Not that that’s any surprise, yours usually are.)
I don’t actually believe we can control our thoughts. What is controllable can be our recognition and assessment of our thoughts, and therefore our response to them, whether we encourage and develop them, or gently (or not-so-gently) dismiss them.
Calls for detachment, learning to panic less readily, and — yes indeed, here come the optimists — learning to smile more readily! 
for today!